The Hall voltage device described in the above patent comprises means included in a magnetic circuit for generating a magnetic field, a cylindrical box mounted between and substantially parallel to the planar boundaries of the air gap defined by the field generating means, which box is arranged to receive a fluid having charged particles distributed therein and which box includes electrodes located adjacent to its axis and its inner periphery, respectively, and adapted to cooperate with the fluid, and means for imparting to the box a rotational movement about its axis, which axis substantially coincides with the central axis of the magnetic circuit. The Hall voltage generated during operation of the device is collected through a pair of mercury contact systems, one of which cooperates with a pivot secured to the box into which the fluid to be examined can be introduced, while the other cooperates with a shaft also secured to the box and adapted to impart the rotational movements of the box during operation.
It has appeared that the collection technique employed with the earlier embodiments of the device is subject to failures which are partly the result of the operation of the device itself. Moreover, the contact system occupies considerable space.
In addition, in the previously disclosed device, the fluid can be introduced into the volume defined within the box only when the device is at a standstill, the fluid being introduced by means of, for example, a hypodermic needle. This method of introduction of the fluid is disadvantageous under certain circumstances if, for example, it is desired to establish a certain physical-chemical system in the box, which system may be composed of, in succession, mercury, calomel and the fluid to be examined.
An object the present invention is to provide an improved structure which permits introduction of fluid while the apparatus is rotating so as to make it possible to establish a physical-chemical sequential system in the box during rotation.
A further object of the present invention is to provide an improved structure of the mercury contact system which lacks the disadvantages of the previously disclosed apparatus.